[21.10] The Power Density Spectrum of the Seyfert 2 Galaxy NGC 4945: The Relationship between X-ray Variability and Black Hole Mass

The nearby Seyfert 2 galaxy NGC 4945 was observed in late
2002 using RXTE for a period of sparse sampling spanning 50
days, including 7 days of intensive monitoring. The
variability of the hard X-ray nuclear flux is clearly seen
in the data, while the mean count rate and the spectrum are
in agreement with previous detections of NGC 4945. We
analyze the variability in the 8 - 30 keV band using several
different methods. By considering the scaling relationship
with the mass of the central black hole, the break in the
power density spectrum is expected at a timescale around 3 -
5 days. Measuring this value reliably using our data will
provide the calibration for the relationship between the
shape of the X-ray power density spectrum and the mass of
the central black hole, which for NGC 4945 is known
independently from megamaser observations.